The present invention relates to a breakaway coupling for a flexible fuel supply hose and of the general type disclosed in U.S. Pat. No. 4,691,941 and in U.S. Pat. Nos. 4,763,683, 5,433,247 and 6,899,131 which issued to the assignee of the present invention and the disclosures of which are herein incorporated by reference. The breakaway coupling may be constructed for a coaxial hose as disclosed in the patents with a fuel supply passage and a vapor return passage both of which have axially moveable valve members for closing the passages in the event the coupling is separated. The present invention also relates to a breakaway coupling having a single fuel supply passage with axially moveable valve members for closing the fuel supply passage in the male and female coupling bodies in the event of separation of the coupling.
In a breakaway hose coupling having a single fuel supply passage or coaxial fuel supply and vapor return passages, the breakaway coupling protects the fuel dispensing equipment from forces which may damage the equipment when separation of the coupling occurs. For example, when a vehicle driver inadvertently forgets to remove the fuel dispensing nozzle from the fuel tank inlet tube and drives away, as discussed in above-mentioned U.S. Pat. No. 4,691,941, the coupling separates when the hose receives a substantial axial tension force, for example, between 200 and 400 pounds. Upon separation, the internal valve members move to their closed positions to prevent the release of fuel from the coupling components and attached hoses.
The female and male coupler bodies are releasably retained together by various means, for example, by a spring biased annular cam pressing against circumferentially spaced balls, as disclosed in above-mentioned U.S. Pat. No. 4,691,941, or by one or more shear pins, as disclosed in above-mentioned U.S. Pat. No. 4,763,683 or by the use of an annular coil spring, such as disclosed in above-mentioned U.S. Pat. Nos. 5,433,247 and 6,899,131. While the use of shear pins is the least expensive means for releasably connecting the coupler bodies, trained repair personnel and significant time is required to replace the shear pins after the coupler bodies have been separated. Since the use of the circumferentially spaced balls and a spring biased cam ring results in an expensive connection of the coupler bodies, the use of an annular coil spring has been adopted to reduce the cost of the releasable connection of the coupler bodies and to permit reconnecting the coupler bodies. However, the use of annular coil springs results in variation in the tension force required to separate or pull the coupler bodies apart. In addition, the annular coil spring connection also requires a significant axial compression force to rejoin or reconnect the coupler bodies. It has also been determined that the hydraulic line shock or hammer effect produced in the fuel supply lines or hoses during shut off of the fuel supply by the dispensing nozzles results in wear of the shear pins and coil springs. This wear reduces the tension force required to separate the coupler bodies and thus requires periodic maintenance or replacement of the pins or springs.